Transcript Characteristics of Simple Worms • Phylum Platyhelminthes is made up of flat worms.

Characteristics of Simple Worms
• Phylum Platyhelminthes is made up of flat worms.
– They have a flattened tube of muscle, simple digestive
system,
a single opening that serves as both mouth and anus.
• Phylum Nemertea are more complex with a flat
shape.
– They have a simple blood vascular system, one-way digestive
system, separate mouth, and anus.
– They are carnivores.
• Phylum Nematoda are
structurally simple round
worms.
– More complex than the other
two phyla. Most are parasitic
worms, some live in sea animals.
– This phylum also includes
human parasite forms.
Special Attributes of Simple
Worms
• Lineus longissimus, a
nemertean, found in the
North Sea is perhaps the
longest known creature in the
world – more than 60 meters
(197 feet).
Features of segmented worms
1. Members of the Phylum Annelida (which
means little rings)
1. Most are in the class Polychata
2. 6000 species of polychata
2. Tube-shaped body divided into segments
(which is where the name comes from)
3. Found:
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Fresh water
Salt water
Moist soil
4. They have a body cavity which holds their
organs
1. Closed circulatory system
2. Crawling worms (2- 4 inches) are carnivores
3. Those that burrow are deposit feeders
5. They all have “Setae”
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Bristle-like structures on the sides of each segment
Helps worms move through the soil and hold on
to the soil
Some have developed gills on these
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The planktonic larval phase is called a
trochophore
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Band of cilia around the body
Some species can reproduce asexually by
fission. Earthworms do NOT reproduce
asexually. They reproduce sexually. They are
hermaphroditic. Other annelids are either
male or female.
Most live in tubes made of mucus, seaweed,
cemented mud, etc
Characteristics of Annelids
• Worms in phylum Annelida stand apart
because of their structural complexity.
– They have a heart, nephridia, and sometimes, jaws.
• Most important, they exhibit metamerism
– the division of the body into repeating blocks or segments.
Special Attributes of Annelids
• Of particular relevance to oceanography – class
Polychaeta, because many polychaete worms live
in the marine environment.
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1. Tubeworms have flower-like “antennae.”
2. Bristleworms sting when touched.
3. Spongeworms live on sponges.
4. Fireworms live on the surface of fire coral.
Other types
1. Oligochaetes = class Hirudinea. They are
earthworm relatives
2. Leeches = most are freshwater, those that are
marine water typically live on another fish.
They have no parapodia
3. Sipunculans = unsegmented bodies and bury
themselves in mud. Exclusively marine and in
shallow waters
4. Echiurans = over 100 species and are
exclusively marine
5. Pogonophora = lack a digestive system
(including mouth and gut). Also known as
beard worms
6. Chaetognaths = one of the smallest animal
phyla. They have eyes, teeth, grasping spines,
transparent and fish like fins and tails
Characteristics of Mollusks
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Phylum Mollusca – the mollusks – ranges
from squid and octopuses to sea slugs,
snails, oysters, clams, and conches.
It has the most species of any other ocean
group
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Making it the most successful at 110,00 species
Immense diversity in structure and habitat
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Can be found in splash zones of rocky shores to
deep sea hydrothermal vents
Can thrive on just about every concievable diet
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Three characteristics all members share:
1. A muscular bag called the mantle.
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A thin layer of tissue that covers the body
– Produces the shell
– Shell is made of CaCO3 to protect its soft body
2. A muscular foot beneath the head (ventral).
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Used for locomotion
3. Most have a head with eyes, sensory organs, and a
radula (a tongue with rough scraping teeth used
for feeding).
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Radula is made of Chitin
– A highly resistant material found in many invertebrate
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Bodies are unsegmented, Bilaterally
symmetrical bodies
All mullusks have the same basic
body plan with some modifications
• Shell is internal in squids and absent in sea slugs
and octopuses
• Portions of the body are coiled and
asymmetrical in snails
• The radula is modified or absent in some
mollusks
Special Attributes of Class
Gastropoda
• Snails, whelks, slugs, and most single-shelled
mollusks belong in class Gastropoda.
• 75,000 species, mostly marine
• Basically a coiled mass of vital organs enclosed by a
dorsal shell
– Shell is usually coiled and rests of the on a ventral
creeping foot
Varied types of feeding
• Use radula to scrape algae from rocks
– Periwinkles, limpets, abalone
• Deposit feeders feed off of soft bottoms
– Mud snail
• Carnivores
– Whelks, oyster drills, cone shells
• They specialize in prey like clams, oysters, worms, and
even small fish
• Violet snails prey on siphonophores
• Sea slugs (nudi-branch) feed off of sponges and hydroids
• They use noxious chemicals and nematocysts
• Torsion is a developmental process.
– It occurs after the veliger settles and begins
maturing. Its body twists into a permanent loop that
rearranges the organs and brings them together
allowing the body to draw into the spiral shell
common to this class.
Class Bivalvia
• Belonging to class Bivalvia (bi meaning two) are
mollusks that have two hinged shells.
– Mussels, clams, oysters, and scallops are all bivalves.
• Has the basic Mollusk structure
– Body is laterally compressed and enclosed in 2
valved shells
– No head nor radula
– Gills used for breathing Oxygen and sorting small
food particles
– Inner surface lined by a mantle
• body lies in mantle cavity
Clams
• Use a shovel-shaped foot to burrow in sand and
mud
• Forms siphons by fusing edge of mantle to draw
in and out water to allow clams to feed and
obtain oxygen while buried in sediment
Mussels
• Do not burrow
– Instead attaches to rocks and other surfaces using
byssal threads
Oysters
• Cement shell to hard surfaces
– Often another oyster
• Pearls form when oysters secretes CaCO3 to
coat an irritant
– Can be particles of sand to parasites lodged between
the mantle and the iridescent
– Cultured pearls are obtained by carefully inserting
bits of shell or plastice
• Some scallops live unattached and
swim for short distance by rapidly
ejecting water from mantle cavity
and clapping valves
• Giant clam is the largest bivalve at
over 1 meter long
• Fouling organism is a common
problem for ocean cities
– Some bivalves attach to wood such as
on boats
Class Cephalopoda
• They are all predators that specialize in
locomotion
– Very agile swimmers, displaying a complex nervous
system
– They have a reduced or eliminated shell
• The basic structure is a head pushed down
toward a foot that has been modified as arms
equipped with suckers to capture prey
• They have eyes that are similar to ours in
structure
• Bodies are protected by a thick muscular mantle
– Elongated in squid, rounded in octopuses
– Mantle forms a mantle cavity enclosing 2 or 4 gills
• They have a structure called a “Funnel”
– Muscular tube formed by what remains of the foot
used as siphon (an exit for water that enters through
a free edge of the mantle
– Used for swimming by forcing water out
• Funnel is flexible allowing it to be relocated
• This class includes cuttlefish, squid and octopuses.
– Cuttlefish (order Sepioidea) differ from squid and
octopuses by having an internal shell used primarily for
buoyancy.
– Squid (order Teuthoidea) differ from cuttlefish and
octopuses with their streamlined, torpedo-shaped
bodies adapted to life in open water.
– Octopuses (order Octopoda) differ from squid and
cuttlefish by having no shell and living in rocky reefs and
coral.
• Octopuses are probably the most intelligent invertebrates.
Biology of Mollusks
Digestion
• Contain a separate anus and mouth
• Digestion involves digestive glands such as
salivary glands that release enzymes which break
down food into simpler molecules
• Circulatory system transports nutrients and
oxygen to cells using a dorsal, muscular heart
– Most mollusk have an open circulatory system
– All cephalopods have a closed system
Differences in digestion
• Chitons and snails use a combination of
extracellular and intracellular digestion
– Snails keep chloroplast intact and continue to carry
put photosynthesis
• Carnivorous snails modify radula to drill and
capture prey. May even have jaws.
– All extracellular
• Bivalves have long strings of mucus in mouth to
trap food
• Crystalline style in stomach rotates food to help
digest
– Contents eventually pass into large digestive gland
for intracellular digestion
• Giant clams contain zooxanthellae that live in
tiny branches of gut that extend into mantle for
extra nutrients
• Cephalopods are entirely extracellular. Stomach
is connected to an extra sac to speed up
digestion
Nervous System and Behavior
• Snails, chiton, and bivalves possess a ganglia
• Cephalopods have a true brain.
– Design of their brain is similar to humans
• Like humans, body is controlled through a
combination of nerve fibers and the brain
– High learning capacity
• Can control color change depending on mood
Reproduction and Life History
• Some are hermaphrodites
• Bivalves, chitons, and some snails fertilize
externally
• Cephalopods and most snails are internal
– Males modify an arm to transfer a spermatophore
– Snails use a long, flexible penis
– Female octopuses protect the eggs until hatched
• Young develop in yolk-filled egg
• Female usually dies after eggs hatch
Arthropods
• Phylum Arthropoda is the most numerous of multicellular
animal phyla.
– There are several intermediate classifications.
– There may be as many as one million arthropod species.
• 3 out every 4 animals is an arthropod
– Characteristics: segmented bodies, jointed legs, a chitinous
exoskeleton.
– Segmented bodies with bilateral symmetry
• Segmentation adds flexibility
– Jointed appendages
• Including the mouth
• Moved by sets of attached muscles
– They have a chitinous exoskeleton
• Secreted by underlying layer of tissue
– Tough, non-living material
Growth
• In order to grow, arthropods must shed their
rigid shells
– Process is known as molting
• Animal takes in water to expand and forms a
new exoskeleton
• Exoskeleton limits size and growth
– Will never be a giant but exoskeleton and joints gives
a successful combination of protection, support,
flexibility, and increase surface area for muscle
attachments
Superclass Crustacea
– an intermediate classification.
– Characteristics include:
• A pair of appendages on each body segment.
– Specialized for swimming
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Two pairs of antennae.
Mandibles for chewing.
Teardrop-shaped larvae.
Exoskeletons are shed
as they grow.
Special Attributes Krill
• Class Malacostraca includes two orders of interest due to their
roles as food for humans and food for nature.
• Order Euphausiacea: krill
– Krill are important primary and secondary consumers that
link smaller plankton to larger consumers.
– In subpolar food webs, they are vital. Whales, seals, sea birds,
and penguins only survive in highly productive waters. Much
of the food web above krill
depends on it for life.
Decapods
• 10 legs
– 1st pair usually has claws to obtain food and defend
• Referred to as cheliped
– Rest of body is divided into the Cephalothorax and abdomen
– Have claws and an extended carapace that encloses the gills.
• Because humans eat these shellfish, they are an important food source
and resource on which the fishing industry relies.
• Includes shrimp, lobster, crabs, hermit crabs
– Hermit crabs are not actual crabs
– Shrimps have laterally compressed bodies and elongated abdomen
like a lobster
• Also scavengers
• Crabs have a broad cephalothorax and a tucked in abdomen
Special Attributes of Class
Cirripedia
• Barnacles unique lifestyle sets them apart into
class Cirripedia.
– Life begins as free-swimming larvae like other crustaceans.
– When the larva finds a surface on which to live (rocks, boats,
etc.) it fuses itself in place “upside down.”
– The exoskeleton forms the carapace (hard shell) the barnacle
can withdraw into for protection.
Special Attributes of Copepods
• Copepods play a central role in the ocean
food webs.
– They are important primary and secondary
consumers of
phytoplankton and zooplankton.
– Relatively few larger animals can consume the
tiniest plankton, but many can eat the larger
copepods. Fish, krill, and giant plankton
feeders, including whale sharks, baleen whales,
and manta rays all eat copepods.
– Copepods are important to ocean food webs
because they link the tiny primary producers
and consumers to the large animals higher
up the web.
Digestion
• Filter feeder
– Stiff, hair like fibers to catch food
• Particles carried by currents caused by other moving
appendages
• Parasitic crustaceans have bristles used for piercing and sucking
– Maxillipeds are the appendages closest to the mouth are
turned upward and specialized to sort out food and push
it in to the mouth
• 3 pairs
– Stomach has chitinous teeth/ridges for grinding and
bristles for sifting
Nervous system and Behaviour
• Small, simple brains that are more centralized in
decapods
• Highly developed sensory organs
– They have compound eyes
• In decapods eyes act as periscope
– Keen sense of smell
– Use a pair of statocysts for balance
• Use signals to communicate with each other
Reproduction
• Generally have 2 genders
– Gametes are rarely shed into water
• Males have a specialized appendages to transfer
sperm
– Even hermaphroditic species
• Usually occurs immediately after female
decapods molts
– Can store sperm for long periods of time
• Nauplius is a common crustacean larva
Characteristics of Echinoderms
• Even though the organisms in phylum Echinodermata don’t at first
look and act much like animals, they are.
– They move. They attack prey. They defend themselves.
They just tend to do so very slowly.
• They all share:
– A radially symmetrical body divided into five parts.
– Most have hundreds of tiny tube feet to crawl and climb.
– Most have a water vascular system that
brings oxygen to the body cells.
• Echinoderms have some traits close
to chordates.
– The adult is radially symmetrical.
– The larvae are bilaterally symmetrical.
Bilateral symmetry, along a vertical axis,
is what mammals, fish, etc. have.
Special Attributes of Crinoids
• Class Crinoidea include feather stars and sea lilies.
• The primary characteristics of this
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– Long feather-like arms and short,
hook-like legs called cirri.
– They have upward-facing mouths.
– Most are nocturnal feeders. At night, they unfurl
their arms to capture plankton and nutrients carried
into their paths by the current.
– By day they coil up tightly and hide in the reef.
– Most crinoids attach to the bottom by their cirri.
Special Attributes of Sea Stars
• Sea stars belong to class Asteroidea.
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They are predators with downward-facing mouths.
They have tube feet covering their undersides.
They usually have five arms.
A few species have toxic spines for protection.
Each arm carries an equal share of the
animal’s systems and organs.
– They can regenerate a lost limb, some grow
into several new animals when cut into pieces.
Special Attributes of Brittle Stars
• Brittle stars belong to
class Ophiuroidea.
– This class has slender legs
that are proportionately
longer and thinner than
those on sea stars.
– Brittle stars feed on
detritus and small
animals.
– They use arms and tube
feet for locomotion.
Special Attributes of Sand Dollars
and Sea Urchins
• Sand dollars and sea urchins are part of class
Echinoidea.
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They have the five-section body, but no arms.
Sand dollars and sea urchins share a disk-shaped body.
They have tube feet on the underside.
Sea urchins graze on algae.
Swimmers avoid sea urchins because of their spines.
• Some species have toxins in the spines for self-defense.
• Urchins can move their spines to assist in locomotion.
Special Attributes of Sea Cucumbers
• Sea cucumbers are part of class Holothuroidea.
– They have an elongated five-segment body
with tentacles around the mouth.
– Most feed by moving with their mouths open, allowing sand
to flow through. A few are filter feeders.
– Some expel a sticky mass of white tubes covered in toxin.
– They are protected by tough skins and by the ability to expel
part of their internal organs for predators while saving the rest to survive.
Digestion
• Carnivorous
– They invert stomach through the mouth to envelope
food
– The intestine is short or missing
– The body cavity is filled with a coelomic fluid
– Also serves to bring in oxygen.
– Sea cucumbers bring in water through the anus to
the respiratory branches
• Extensions of gut
Reproduction
• They have separate sexes with 5, 10, or more
gonads that shed sperm or eggs
– Spawning
– Gametes do not survive long in the water
• Individual spawn all at once
– Fertilized egg develop into the plankton and results
in a ciliated larva
• Some echinoderms carry eggs
• Asexual reproduction
– Fission
• The central disk splits
into 2 new individuals
– Regeneration
• The ability to grow
missing parts
• Requires that part of the
central disk be present to
grow a new individual
• Sea star do not require
the disk